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tty: Define ASYNC_ replacement bits

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Prepare for relocating kernel private state bits out of tty_port::flags
field; tty_port::flags field is not atomic and can become corrupted
by concurrent updates. It also suffers from the complication of sharing
in a userspace-visible field which must be masked.

Define new tty_port::iflags field and new, substitute bit definitions
for the former ASYNC_* flags.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2016-04-09 17:53:20 -07:00 • committed by Greg Kroah-Hartman
parent 97ef38b821
commit e4d38f334a
2 changed files with 23 additions and 2 deletions
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16
include/linux/tty.h
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@ -228,7 +228,8 @@ struct tty_port {
int count; /* Usage count */
wait_queue_head_t open_wait; /* Open waiters */
wait_queue_head_t delta_msr_wait; /* Modem status change */
unsigned long flags; /* TTY flags ASY_*/
unsigned long flags; /* User TTY flags ASYNC_ */
unsigned long iflags; /* Internal flags TTY_PORT_ */
unsigned char console:1, /* port is a console */
low_latency:1; /* optional: tune for latency */
struct mutex mutex; /* Locking */
@ -242,6 +243,19 @@ struct tty_port {
struct kref kref; /* Ref counter */
};
/* tty_port::iflags bits -- use atomic bit ops */
#define TTY_PORT_INITIALIZED 0 /* device is initialized */
#define TTY_PORT_SUSPENDED 1 /* device is suspended */
#define TTY_PORT_ACTIVE 2 /* device is open */
/*
* uart drivers: use the uart_port::status field and the UPSTAT_* defines
* for s/w-based flow control steering and carrier detection status
*/
#define TTY_PORT_CTS_FLOW 3 /* h/w flow control enabled */
#define TTY_PORT_CHECK_CD 4 /* carrier detect enabled */
/*
* Where all of the state associated with a tty is kept while the tty
* is open. Since the termios state should be kept even if the tty